1. Field of the Invention
The present invention relates to a method and system for detecting a void around a buried pipe or conduit, and in particular, a method and system for void detection using acoustic resonance.
2. Background of the Invention
Voids around a buried conduit (e.g., pipe) are gaps between the exterior surface of buried conduit walls and the backfill material covering the conduit. Voids surrounding a buried conduit may pose potential problems to the conduit and a system employing the conduit. For example, voids around pipelines allow water to flow therethrough which may lead to damage of the pipeline and associated systems. Therefore, it is advantageous to detect voids in an effort to avoid potential damage such as these and others.
Current systems for detecting voids around buried conduits include manual, visual inspection of the backfill material and the exterior of the conduit or a pipeline. One obvious major disadvantage of using visual inspection to detect voids around buried conduit is that various portions of the conduit may be inaccessible for visualization.
In accordance with the present invention, a void in backfill material, such as soil surrounding a buried conduit may be detected from an acoustic frequency response of the conduit resulting from acoustic excitation of the conduit. By comparing the acoustic frequency response to a baseline frequency response range, a void is detected as an acoustic frequency response outside a baseline frequency.
According to one aspect of the invention, a method is provided for detecting a void outside a buried conduit. The method includes providing acoustic excitation of an interior portion of the conduit and detecting an acoustic frequency response of the conduit resulting from the acoustic excitation. The acoustic frequency response is compared to a baseline frequency response range. The void is identified when the acoustic frequency response is outside the baseline frequency response range.
According to another aspect of the invention, a system for detecting voids in backfill material around a buried conduit includes an acoustic exciter adapted for applying acoustic energy to an interior portion of the conduit. An acoustic frequency sensor detects a frequency response of the conduit resulting from the acoustic energy. A processor compares the acoustic frequency response to a baseline frequency response range and identifies the void as an acoustic frequency response outside the baseline frequency response range.
An advantage of the present invention relates to the use of detected resonant frequencies produced in a buried conduit in response to acoustic excitation to detect a void outside the buried conduit.
Another advantage of the present invention relates to the detection of a void outside a buried conduit where visual inspection of the void is not readily available or possible.
A further advantage of the present invention relates to determining the integrity of the backfill material surrounding a buried conduit. The present invention allows for the monitoring changes in acoustic frequency responses from a buried conduit resulting from applied acoustic excitation. As a result, integrity of the backfill material may be tracked as changes or variations in the acoustic frequency response.
Further features and advantages of the present invention will be set forth in, or apparent from, the detailed description of preferred embodiments thereof which follows.